1. Field of the Invention
This invention relates in general to earth boring bits of the type having fluid nozzle openings for communicating drilling fluid to the bit face, and in particular to a method of hardfacing a steel bodied bit to prevent erosion by fluid communicated through the nozzle openings.
2. Description of the Prior Art
An earth boring bit of the type concerned herein has a body with a threaded pin on its upper end for connection to a string of drill pipe extending to the surface. The bit has a cutting face on its lower end, which is an integral part of the body. Polycrystalline diamond (PDC) disk cutting elements are mounted on the face by studs received in holes provided in face. Normally, there are several passages extending through the body for discharging drilling fluid pumped down the drill string. Nozzles are located at the outlets of the passages. The nozzle is normally of tungsten carbide to resist erosion.
In the past, steel bodied bits of the type under consideration were hardfaced by using "plasma spray" or "detonation gun" processes. These techniques are "line of sight" processes, in that the hardfacing material is hurled at the target substrate at high velocity, making it impossible to hardface the interior of the nozzle openings satisfactorily. As a result, the prior art bits were subject to erosion or undermining of the hardfacing on the bit face near the nozzle openings due to the flow of drilling fluid past the unhardfaced areas.